Interior Basement Insulation – XPS vs EPS selection – Ordering material today!
I’ve read the blog post here https://www.greenbuildingadvisor.com/blogs/dept/musings/how-insulate-basement-wall
Before I finalize my decision and place order today I am hoping to get some reassurance / advice. I am finishing my 2500 sqft basement which has poured concrete walls. I originally was going to do 2″ XPS on perimeter of wall (Pink Stuff) and 1″ XPS foamular 150 on floor with T&G OSB or plywood sub floor on top. However when at HD, I saw a product called DuroSpan, also goes under the label DuroFoam in Canada, that is 2″ EPS with foil like film on both sides which cost almost $10 less than XPS. I was considering using this product for the walls, however decided against it because I am concerned the foil like lining would permit any moisture from concrete wall from being absorbed and dry inward. Although XPS has a low permeability, my thought is at least if some minor leakage did occur from a hair line crack at least it could be absorbed and dry inward, otherwise, if / when there is a minor water leak where would the water actually be able to dry to? However now I have found 2″ closed cell EPS non-faced R8 for only $10 / sheet which would be over $15 savings per 4×8 sheet, being I need over 70 sheets this is a significant savings. My thought is the un-faced EPS would allow moisture / water to be absorbed in the event of a minor leak and dry inward, plus save me over $1,000 on material. For the concrete floor I would still use 1″ XPS (Pink stuff), and have found the Foamular 250 as opposed to the formula 150 for even greater compression strength for only a $1 to $2 per sheet more. Am I missing anything? Will the EPS perform as good or better in this installation? XPS would be R10, EPS is R8, however I will be framing and filling stud cavity with batt insulation anyways. I will attempt to link to the EPS I am considering here: https://www.menards.com/main/building-materials/insulation/insulation-panels/expanded-polystyrene-foam-insulation-2-x-4-x-8-r-8/p-1444435971902-c-5779.htm?tid=-1979961929525189151&ipos=1 – Thank you for any insight back. I appreciate it. (Also I live in Climate Zone 5 in South East Michigan, however I don’t think that is relevant to my question.)